Does the layer thickness mean same as Z-axis precision? yes and no. Layer height is how much each layer should be. Precision is how close a machine maintains that.
I think its the linear system that people adopt in their builds that mainly contributes to the best possible print quality when you consider most of them use the same components. The other small hardware differences like hot and cold ends should be looked at also.
Reprap evolves all the time but not all reprappers keep up with the evolution.